Many metal oxides and other metal-based compositions are known as heterogeneous catalysts for gas and liquid phase oxidation and reduction reactions in the chemical process and petroleum refining industries. However, these catalyst compositions often deteriorate in use, losing their crystallographic identity or active components through volatilization, poisoning or crystallite growth.
For example, catalytic reforming requires catalysts that provide active acidic sites such as halogen. These acid sites in conventional reforming and hydrocracking catalysts are continuously lost during operation, with concomitant loss in catalyst utility.
Moreover, current environmental concerns require catalysts capable of converting the objectionable components of industrial and automotive exhaust streams to innocuous substances. Known catalysts have generally been unable to withstand the reducing atmospheres, high temperatures, and anti-knock additive residues commonly found in such applications.